Gelatin filter in Canon 17 40L

[Sendide]

dear 17 40 L owners,
Could anyone explain to me please what a gelatin filter does or could do in the back of the canon 17 40 L canon zoom lens. I was reading the booklet that comes with and didn't get it, moreover, they even mention that adding it would cause some gost of flair effect !!!!
thanks in advance

[PhotosGuy]

Gelatin filters are 3” square, or larger, & look like thin plastic, although they aren’t as durable as that. Used to be a cheap alternative to glass when you needed a weird filter, or wanted to put one behind the lens of a view camera for color correction. 8X10” color film was (is) expensive & each emulsion batch often needed some color compensation, especially during loooong exposures (+4 minutes).
I saw some in a cam store the other day & the little suckers were over $10 now, & given their life expectancy, wonder why you think you need them?
Then there’s the problem of how you’re going to attach it & not have it fall off in the body? There are screw on filter holders for the lens, but you’re looking at a bigger opportunity for flare if you do that, too.
My advice, unless there’s some compelling reason to use them, is to forget it!

[slin100]

Get the Roscolux Swatchbook (http://www.bhphotovideo.com/bnh/controller/home?O=WishList.jsp&A=details&Q=&sku=45189&is=REG) . It's a sampler of mostly colored filters (also includes a few ND filters). I bought (it's only $.01, so it's practically free!) it to filter my shoe-mount flash. Work great!

You can cut out small square and slip it into the filter holder on the 17-40L.

[Sendide]

thanks for the reply,
I don't need this filter :) jsut wnated to know what it can do and where does it help
regards
Khalid

[Mark Kemp]

In simple terms its a bit of translucent coloured plastic and it makes your pictures look a bit soft and a turns them a funny colour. So if you want funny coloured pictures they are ideal otherwise don't bother.

[Canuck]

I have a pic of the back of the 16-35mm F2.8L lens that has the outline of what you'd want to cut it to be and where it goes. I can add that pic to this one if you like.